1. Field of the Invention
This invention relates to a method using a cantilever to measure physical properties
2. Description of the Prior Art
The atomic force microscope (G. Binnig, C. F. Quate and Ch. Gerber, Phys. Rev. Lett. 12, 930, 1986) is an example of an apparatus that uses a cantilever to measure minute irregularities on the surface of a sample. The atomic force microscope is a new type of microscope which images irregularities within a minute region by utilizing the deflection induced in a cantilever supporting a tip owing to the force acting between the sample surface and a probe. Methods have been proposed for using the atomic force microscope to measure the defect distribution, elasticity and other physical properties of a sample by detecting the vibration induced in the cantilever when the sample is vibrated at a much higher frequency than its fundamental resonance frequency [K. Yamanaka, H. Ogiso and O. Kolosov: Appl. Phys. Lett. 64, 178 (1994) and U. Rabe and W. Arnold: Ann. Physik 3,589 (1994)]. These methods can measure the elasticity of hard materials, which is not possible with the force modulation method in which the sample is vibrated at a frequency about the same as or lower than the fundamental resonance frequency of the cantilever [(M. Radmacher, R. W. Tillmann, and H. E. Gaub: Biophys. J. 64, 735 (1993)].
Since these prior-art methods vibrate the sample at high frequency, however, the sample has to be bonded to an ultrasonic vibrator. This bonding involves various problems:
(1) The optimum bonding agent has to be selected for each type of sample. Thickness variations and bubbles occurring in the bonding agent cause uneven vibration and degrade measurement reproducibility. PA0 (2) Bonding agents are a cause of sample contamination and cannot be used with LSI wafers and other such samples requiring a high degree of cleanness. PA0 (3) A large or irregularly shaped sample is hard to vibrate uniformly by contact with a vibrator. The method of bonding the sample to the vibrator can therefore not be used for inspecting such industrially important components as large LSI wafers, magnetic heads and bearings.
This invention was accomplished in response to the foregoing circumstances and has as one object to provide a method which uses a cantilever to measure physical properties with high reproducibility, specifically to such a method which, without requiring the sample under examination to be bonded to a vibrator, achieves the same effect as when the sample is vibrated.
Another object of the invention is to provide a method which uses a cantilever to measure physical properties, specifically to such a method which can be readily applied to measure the physical properties of a sample requiring a high degree of cleanness or a sample of large size or irregular shape.
In this specification, "measurement of physical properties" and similar expressions are defined to include the measurement of the distribution of defects at and in the vicinity of the sample surface and the measurement of sample elasticity.